STAg和霍乱毒素不同程序滴鼻免疫小鼠诱导抗弓形虫作用

Immune Responses of Mice to Intranasal Immunization with CT Adjuvant and STAg Against Toxoplasma gondii Infection

目的观察弓形虫可溶性速殖子抗原(soluble tachyzoite antigen,STAg)和霍乱毒素(cholera toxin,CT)佐剂不同程序滴鼻免疫小鼠诱导的抗弓形虫感染能力,确定STAg和CT滴鼻免疫的最佳程序。方法BALB/c小鼠随机分为3组:1次、2次和3次免疫组,用20 μg STAg+1 μg CT/只分别滴鼻免疫1次,2次或3次,前2次间隔2周,末次间隔1周。末次免疫后第14天,用4×104个速殖子/只灌胃攻击所有小鼠,观察小鼠健康及死亡情况,攻击后第30天处死,ELISA法检测血清IgG和粪便IgA,计数肝、脑组织内弓形虫速殖子,分离并计数派伊尔结(Peyer′spatches,PP)和脾淋巴细胞数。结果2次和3次免疫组小鼠存活率明显高于1次免疫组(P<0.05),肝、脑组织内虫荷显著低于1次免疫组(P<0.001),血清IgG和粪便IgA高于1次免疫组,PP和脾淋巴细胞数无显著性变化。结论STAg和CT佐剂滴鼻免疫2次或3次能有效诱导小鼠抗弓形虫感染。

Objective To optimize the procedures for the induction of protective immunity in mice after intnmasal immunization with CT adjuvant and STAg from Toxoplasrna gondii. Methods BALB/c mice were divided into 3 groups （A, B and C）. Mice in Group A were intranasally immunized once with 20 μg STAg and 1 μg CT. Mice in Group B were immunized with the same concentration of STAg and CT at day-0 and day-14. Mice in Group C were immunized with the same antigen preparation at day-0, day-14 and day-21. All mice were challenged intragastrically with 4×10^4 tachyzoites on day-14 after the last immunization. The survival of mice was monitored after the challenge. The liver, brain, Peyer＇s patches and spleen were removed at day-30 after the challenge. The numbers of tachyzoites in the livers and brains were counted. Levels of serum IgG and IgA in feces were determined by ELISA. The numbers of lymphocytes in spleen and Peyer＇s patches were counted. Results Mice in Group B and Group C had a higher survival rate than the mice in Group A （P〈0.05）. The increase in survival is correlated with the elevated levels of IgG and IgA （P〈0.05）. The loading of tachyzoite in livers and brains was also significantly lower （P〈0.001）. However, there was no significant difference in the lymphocyte counts in Peyer＇s patches and spleen. Condusion Intranasal immunization twice or three times with STAg and CT adjuvant can induce protective immunity against Toxoplasma gondii, and a booster immunization at day- 14 after the first immunization may be sufficient for the induction of protective immunity.